Beam type electron tube



Jan. 10, 1961 F. J. PlLAS 2,967,967

BEAM TYPE ELECTRON TUBE Filed Sept. 29, 1958 2 Sheets-Sheet l 1N VENTOR.

Fm J P113145 Jan. 10, 1961 F. J. PlLAS 2,957,967

. BEAM TYPE ELECTRON TUBE Filed Sept. 29, 1958 2 Sheets-Sheet 2 A m mmw m 1 N INVENTOR.

- FRANK J PJLAS Unite States Patent BEAM TYPE ELECTRON TUBE Frank J. Pilas, Lyndhurst, N .J assignor to Radio Corporation of America, a corporation of Delaware Filed Sept. 29, 1958, Ser. No. 763,855 9 Claims. (Cl. 313299) This invention relates to beam type electron tubes and particularly to the beam forming electrode thereof.

Beam type tubes are well known in the art and incorporate a beam forming electrode to cause the electron stream to be focused into a beam. This creates a space charge in the screen grid-anode region thus preventing secondary electrons from traveling back to the screen grid. The beam forming electrode generally comprises a pair of spaced apart sheet metal plates and a minimum (so as not to give rise to unnecessary interelectrode capacitances) of interconnecting members to give integrality to the electrode structure. Such an electrode is assembled in an electrode cage so that the two plate elements thereof are disposed one on each side of the beam path, either perpendicular to the beam path or slightly angled relative thereto in funnel fashion.

Included in the design considerations of beam type electron tubes are three particular interelectrode capacitance measurements. These are the capacity of: (1) control grid to anode, (2) control grid to all other electrodes, and (3) anode to all other electrodes. To simultaneously provide a rugged electrode structure, keep these capacities to the desired minimum, and provide the necessary interelectrode shielding, has not been adequately achieved with prior art beam forming electrode designs. Moreover, in automatic machine fabrication of beam type tubes, difliculty is encountered in mechanically handling beam forming electrodes of prior art design since they tend to nest and jam together when stacked in loading chutes for automatic loading onto assembly jigs. Such nesting and jamming has largely been due to the peculiar open type design of prior art electrodes and to their attendant fragility which results in deformed electrodes. Such deformity consequently prevents the electrodes seating in place on the assembly jig.

It is therefore an object of this invention to provide a novel and improved beam forming electrode which can be stacked with others of its kind without nesting or jamming therewith, which is extremely rugged, and which yet provides good shielding between various of the tube electrodes without resulting in undesirable interelectrode capacitances.

Briefly, according to the invention, a beam forming electrode comprises a box-like sheet metal structure having the major central portions of each of its six sides open or removed to provide a box-like frame. The beam forming electrode is assembled with a flat two-sided cathode centrally therein. In operation, the two opposite sides of the electrode facing the two active surfaces of the cathode perform a beam forming function.

In the drawings:

Fig. 1 is a side elevation view of a beam type electron tube incorporating the invention;

Fig. 2 is a transverse section view of Fig. 1 taken on line 2-2;

Fig. 3 is an exploded perspective of the electrode cagev 2,967,967 Patented Jan. 10 1 951 2 of the tube of Fig. 1 showing the novel beam forming electrode thereof;

Fig. 4 is a perspective view of a number of the novel beam forming electrodes stacked in a loading chute.

In Figs. 1 and 2, an electron tube 10 incorporating the invention is shown to comprise an envelope 12 closed at one end with a steam 14 having a plurality of leadins 16 sealed therethrough on which an electrode cage 18 is mounted. The electrode cage 18 includes a pair of mica spacers 19 between which a cathode 20, a control grid 22, a screen grid 24, a novel beam forming electrode 26, and an anode 28 are mounted. The anode 28 comprises a pair of electron receiving portions 30 joined by a connector 32. The novel beam forming electrode 26, as well as the other electrodes of the cage 18, is illustrated in greater detail in Fig. 3.

Fig. 3 illustrates the electrode cage 18 of the tube 10 in exploded perspective. The cathode 20 comprises a flat box-like structure having portions of the major surfaces thereof coated with electron emissive material 34.. The control grid 22 and the screen grid 24 comprisehelical wire wound structures mounted on pairs of side rods 36 and 38, respectively. The novel beam forming: electrode 26, which will be more fully described herein after, includes four mounting tabs 40 which extend par-- allel to the longitudinal axis of the completed electrodecage 18. The two electron receiving portions 30 of the anode 28 are supported in spaced apart parallel planes; by the connector 32 and are each provided with a pair of mounting tabs 42. The mica spacers 19 are identicali with each other and include along a central line a cen-- trally located rectangular cathode-receiving aperture 44' flanked on each end thereof by a pair of circular aper tures 46 and 48 for receiving the side rods 36 and 38 of"? the control and screen grids respectively, and large' rec--- tangular recesses 50 in the edges of the spacer for re--- ceiving the beam forming electrode tabs 40. Two addi-'- tional apertures 52 for receiving the anode tabs 42 are; provided on a line with the cathode aperture 44 trans---- verse to the line of the other apertures.

In the fabrication of the electrode cage 18, a mica: spacer 19 is first deposited on an assembly jig (not; shown) and the side rods 36 of the control grid 22 in-- serted through the pair of accommodating apertures 46L Next, the cathode 20 is inserted in its aperture 44 and. then the side rods 38 of the screen grid 24 in their aper-- tures 48. The novel beam forming electrode 26 is then: disposed over the cathode and grid electrodes such that: a pair of the mounting tabs 40 are received in the recesses 50 of the mica spacer 19. Next, the tabs 42 of? the anode 28 are inserted in the anode apertures 52.. Following this, the unsupported ends of all of the elec-- trodes mounted on the first mica spacer 19 are aligned. by a pair of gathering tools (not shown) and the top secure them into place and complete the electrode cage 18.

The beam forming electrodes 26 comprising a part of the electrode cage 18, can be seen from Fig. 3 to resemble a rectangular sheet metal box having central portions of each of its six side surfaces cut away. As such, the beam forming electrode 26 is essentially constituted of twelve legs, all integral with each other, with each leg lying along one of the twelve edges of a rectangular box. When assembled into a cage 18, four of the twelve legs comprise members parallel to the cathode 20 and constitute two pair of beam forming plates 54. Each pair of these beam forming plates define one of two parallel planes. In the assembled tube, the beam plates 54 are so disposed that each one of a pair thereof lie on each side of a beam path substantially perpendicular thereto. The remaining eight of the twelve legs comprise two sets of four legs 56 with each set of four serving to intercom nect adjacent ends of the four beam plates 54. Each set of four legs is efiectively constitued simply by an apertured metal sheet. Accordingly, table-like end surfaces 58 are provided for the electrode 26 so it can be stacked with others of its kind without nesting and jamming there with. Such complete interconnecting of the beam plate legs 54- prevent any elemental parts of the electrode 26 from flexing apart to permit one electrode to telescope down over another such electrode. This non-nesting feature is illustrated in Fig. 4.

In Fig. 4, a number of the beam-forming electrodes 26 are shown end-on-end in a loading chute 60 as would be encountered in conventional automatic loading of electrodes onto assembly jigs. The mounting tabs 4% on the ends of the electrodes 26 rest against the table-like end surface 58 of the adjacent electrode to prevent a nesting and consequent jamming between adjacent electrodes. In the absence of such interconnecting table-like surfaces, the elemental leg members of an electrode may be distorted just enough to permit one electrode to telescope down over an adjacent electrode and jam therewith. It will be appreciated that nesting is prevented by virtue of the four interconnecting leg members 56 at one end of the beam plate legs 54 being disposed as a flat table-like surface 58 relative to the mounting tabs 40 of an adjacent contacting electrode rather than as edge surfaces from interconnecting legs arranged parallel with the mounting tabs 49 of an adjacent electrode. It is this feature therefore which makes possible automatic machine feeding of the beam-forming electrodes 26.

According to a preferred manner of constructing the electrode 26, a sheet metal member has stamped therefrom in an appropriate pattern, a part which can then be folded to form a six-walled member and thereby constitutc the beam-forming electrode 25. According to such manner of fabricating the electrode 26, one pair of beam plate legs 54 are comprised of two half sections 62 and 64, the ends of which are brought together and folded together in a lock seam 65 to form a complete beam plate leg 54.

In order to reduce interelectrode capacitance between the beam forming electrode 26 and the anode 23, each of the four beam plates 54 is centrally concavely contoured along its outer edge by virtue of an arcuate cutaway 66. A reduction in capacitance is thus effected because of the reduced area of the beam plates 5 and because of the increased distance between the beam plates 54 and the anode connector 32. Actually only the two of the four beam plates around which the anode conhector 32 lies need to be so contoured. However, all four of the bear forming legs 54- are cut away so that the anode connector can be disposed around either of two sides of the beam forming electrode 26. This facilitates loading by dispensing with one requirement of orientation.

It will also be appreciated that by virtue of the completely interconnected box-like frame structure of the novel beam-forming electrode 26, an exceptionally rigid electrode is provided. Such feature has proved to be an essential one in machine loading of electrodes. Moreover, this completely interconnected box-like frame structure of the electrode 26 results in added shielding between electrodes by virtue of the two table-like end surfaces 55.

Prior art efforts to provide a rugged beam forming electrode structure have been mainly directed to making the already known type designs out of heavier material. This is particularly true with the conventional open-ended type structures where the four-beam plates have one free end which are not interconected. Since such structures are unrigidified at one end, even though made of heavier material, the beam plat s cannot be narrowed down to reduce capacitance because to do so would make the structure too weak and flexible. As hereinbefore stated, such flexibility in an open-ended structure promotes nesting and jamming. Thus, ruggedization and capacity minimization have constituted conflicting considerations. Combining or modifying of prior art designs to meet the requirements of simultaneously providing a rugged beamforming electrode having machine loadability and good electrical characteristics have thus failed.

The beam-forming electrode 26 according to my invention solves this dilemma since ruggedization is achieved not simply by making the electrode of heavier material. Rather, a novel box-like structure is provided which gives added rigidity at both ends of the beam plate elements so they can be centrally narrowed down to increase their spacing from the anode connector strap 32. Such design of the beam-forming electrode 26 of my invention is consistent with the considerations of the three electrode capacitances involved in beam-type electron tube design as previously mentioned. The cutting away of the beam plates 54 increases spacing between the beamforming electrode 26 and the anode connector 32 thus reducing the capacitance therebetwcen. This, of course, reduces the capacitance between anode and all the other electrodes, one of the basic design considerations. On the other hand, the two other capacitance measurements considered in beam-type electron tube designe, i.e., control grid to anode capacitance and control grid to all other electrodes capacitance, is not adversely affected since adequate shielding for minimizing these capacitances is provided by the conventional screen grid 24 and the table-like end plate surfaces 58 of the novel beam-forming electrode 26.

It will thus be seen that conflict in design considerations encountered in prior art beam-forming electrode designsare avoided according to my invention. At the same time the beam forming electrode 26 according to my invention provides superior loadability qualities and permits stacking of the electrodes without the problem of nesting and jammin".

What is claimed is:

1. A sheet-metal electrode adapted to be stacked endon-end with others of its kind without nesting and jamming comprising a box-like frame structure including in parallel disposition a pair of rectangular apertured end plates, and two pair of parallel, elongated, coextensive, sheet metal beam plate legs joined to said pair of end plates substantially at their corners and supporting said end plates in spaced mutual overlying registry, each of said pair of legs lying in one of two parallel planes.

2. A box frame type beam-forming electrode for beam type electron tubes adapted to be stacked generally coaxially end-on-end with others of its kind without nesting and jamming therewith, said electrode comprising an integral folded sheet metal structure including two pairs of elongated, coextensive sheet metal beam plates, each pair defining one of two parallel planes, and two sets of four sheet metal legs interconnecting said beam plates at each of their adjacent ends, at least two legs of each set of four legs lying in a plane perpendicular to the axis of elongation of said beam plates.

3. A box-type beam-forming electrode according to claim 2, wherein each of said beam plates is cut away centrally thereof along a portion of the edge therof remote from the other beam plate of its pair.

4. A beam-type electron tube comprising a cathode having two electron emissive surfaces; an anode having two electron receiving surfaces facing said cathode emissive surfaces and defining therewith two electron paths; and a beam-forming electrode comprising four elongated sheet metal beam plates disposed coextensive and parallel to each other in two pairs with each pair defining one of two parallel planes, and two apertured sheet metal plates, at different one of said apertured plates interconnecting adjacent ends of said beam plates, the beam plates of each of said pairs being disposed on opposite sides of one of said electron paths.

5. A beam-type electron tube according to claim-4, wherein each of said beam plates is centrally narrowed by a cut-away portion along a portion of its edge remote from said beam paths.

6. A beam type electron tube according to claim 4, and wherein the beam plates disposed on at least one side of said beam paths are centrally narrowed by a cutaway portion along a portion of their edges remote from said beam paths.

7. A beam type electron tube according to claim 4, and wherein the beam plates disposed on at least one side of said beam paths are centrally narrowed by a cutaway portion along a portion of their edges remote from said beam paths, and wherein said anode includes a connector attached to and extending between said electron receiving surfaces around one side of said beamforming electrode adjacent said cutaway beam plates.

8. An electrode cage for a beam-type electron tube comprising a pair of spaced insulator spacer plates, an elongated cathode and grid mounted between said spacer plates and arranged to provide two electron beam paths, an anode mounted between said spacer plates and including a pair of electron receiving surfaces disposed in said beam paths, and a beam-forming electrode comprising a box-like frame including twelve legs arranged generally as the twelve edges of a rectangular box, one set of four parallel legs comprising two pair of beam plates, each pair lying in one of two opposite planar sides of said rectangular box, each of the two sets of adjacent ends of said beam plate legs being joined by a set of four rectangularly arranged legs at least one of which comprises a table-like end surface perpendicular to said beam plate legs, at least two adjacent beam plates comprising one beam plate of each pair thereof being concavely contoured along a portion of their edges remote from said beam paths, said anode including a connector attached to and between said electron receiving surfaces and extending around one side of said beam-forming electrode in proximity to said concavely contoured beam plates.

9. An electrode cage for a beam-type electron tube comprising a pair of spaced insulator spacer plates, an elongated cathode and grid mounted between said spacer plates and arranged to provide two electron beam paths, an anode mounted between said spacer plates and including a pair of electron receiving surfaces disposed in said beam paths, and a beam-forming electrode comprisinng an integral folded sheet metal rectangular box-like frame incluing twelve legs arranged generally as the twelve edges of a rectangular box, one set of four parallel legs comprising two pair of beam plates, each pair lying in one of two opposite planar sides of said rectangular box, said beam plates being concavely contoured along a portion of their edges remote from said beam paths, the two sets of adjacent ends of said beam plate legs being joined by a set of four rectangularly arranged legs, at least two legs of each set of four rectangular legs lying in a plane perpendicular to the parallel axis of said beam plates.

References Cited in the file of this patent UNITED STATES PATENTS 2,487,592 Rishell Nov. 8, 1949 UNITED STATES PATENT OFFICE CERTIFICATE- OF CORRECTION Patent, No, 2,967,967

Frank J. Pilas January 10 1961 It is hereby certified that error appears in the above numbered paten'b requiring correction and. that the said Letters Patent. should read as "corrected below.

Column i2. line 7, for "steam" read stem after "top" insert mica spacer 19 is then placed electrodes to line 57 for "electrodes" read M column 1, line 23, for "des igne" read -9 design for "therof" read vthereof column 6, lines 14 "comprisinng" read comprising line 5 1, over these electrode line 60, and 15 for Signed and sealed this 26th day of September 1961.

I (SEAL) Attest:

. DAVID L. LADD Commissioner of Patents USCOMM-DG 

